In 1997, the Institute of Electrical and Electronics Engineers (IEEE) approved 802.11 the first internationally sanctioned wireless local area network (WLAN) standard. The IEEE 802.11 standard establishes specifications for the parameters of both the physical (PHY) and media access control (MAC) layers of the network. The IEEE ratified the original 802.11 standards as the standard for WLANs. The initial standard provided 1 Mbps and 2 Mbps transmission rates. This rate of transmission was not sufficient for most general business applications and consequently the rate of adoption was slow.
Recognizing the need for faster transmission speeds, the IEEE ratified the 802.11b standard to allow for transmission speeds of up to 11 Mbps. The new standard aligns wireless connectivity on comparable levels to wired Ethernet LANs. The range for WLANs depends largely on the medium by which the radio waves are transmitted and the strength of the transmitting antenna. Ranges in open air are much longer than in areas comprising several walls between antennas. Depending on the type of radio antenna (omni-directional, bi-directional, etc.) and transmitter strength, optimal distances can vary from 200 feet to 10 miles. Fallback speeds of 5.5, 2, and 1 Mbps occur when optimal distances for transmission are exceeded.
The first 802.11 standard proposed three implementations for the Physical Layer (PHY): Infrared (IR) Pulses Position Modulation, RF Signaling using Frequency Hopping Spread Spectrum (FHSS), and Direct Sequence Spread Spectrum (DSSS). Two working groups were established to explore alternate implementations of the 802.11 standard. Working Group A explored the 5.0 GHz band, while Working Group B focused on the 2.4 GHz band. Wireless communications take place within an area known as the Basic Service Area defined by the propagation characteristics of the wireless medium. A wireless node communicates via a Basic Service Set (BSS) within a basic service area. There are two basic service sets: independent and infrastructure. The independent service set allows wireless stations to operate in a peer-to-peer or ad hoc mode. In the ad hoc network, computers are brought together to form a network “on the fly.” There is no structure to the network; there are no fixed points; and usually every node is able to communicate with every other node. Although it seems that order would be difficult to maintain in this type of network, algorithms such as the spokesman election algorithm (SEA) have been designed to select one wireless node as the base station (master) of the network with the others being slaves. The infrastructure service set is the more common approach involving access points (APs) that allow for and control access to the wireless network. An access point usually contains a transceiver, a wired network interface (e.g., 802.3) and software for data processing. If service areas of access points overlap, handoffs of wireless clients between access points can occur.
Wireless local area networks (WLANs), need their air space to be consistently mapped in order to maintain optimum speed and reliability. In an Ethernet LAN (IEEE 802.3), the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol establishes how simultaneous transmissions (packet collisions) are handled. In a WLAN, collision detection in this manner is not possible due to what is known as the “near/far” problem: to detect a collision, a station must be able to transmit and listen at the same time. To account for this difference, the 802.11 protocol uses a slightly different protocol known as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) or the Distributed Coordination Function (DCF). CSMA/CA attempts to avoid packet collisions by using explicit packet acknowledgement (ACK), which means that an ACK packet is sent by the receiving station to confirm that a packet arrived intact. CSMA/CA works by having the transmitting wireless station sense the air. If there is no activity detected, the transmitting wireless station will wait an additional random period of time. If there still is no activity, the wireless station transmits the data. If the packet is received intact, the receiving station will send and ACK frame that, once received by the original sender, completes the transmission. If the ACK command is not received in a specified random period of time, the data packet will be resent, with the assumption that the original packet experienced a collision. CSMA/CA will also handle other interference and radio-wave related problems effectively, but creates considerable overhead.
Given the collision avoidance mechanisms employed in 802.11-compliant wireless networks, management and monitoring of the wireless network airspace is critical to the performance of the wireless network environment (for example, to ensure that wireless access points do not interfere with one another). The administrative or management functionality associated with WLAN networks, however, generally lacks a reliable and accurate means of collecting, storing, and relating airspace data. Hand-held scanners, AP startup scans, or full-time scanning devices are the current methods of obtaining WLAN air space data. However, these methods are inherently flawed or not cost effective. Accordingly, most WLANs do not perform at optimum speed due to overlapping channel interference and rogue access points (i.e., access points installed without authorization and/or knowledge of a network administrator).
In light of the foregoing, there exists a need in the art for methods, apparatuses and systems that allow for efficient mapping of the air space associated with wireless networks. A need further exists for methods, apparatuses and systems that facilitate detection of rogue or unauthorized wireless access points.